Detection of a driver's status in a vehicle is used for deciding whether the driver is under a condition of safe driving. Briefly, it is an effective means to prevent a traffic accident such as sleepy driving or aside driving. Especially, a gaze clearly represents the driver's conscious condition. Accordingly, a technique to detect the gaze is very effective.
In the prior art, as a method for detecting a user's gaze direction, a first method using a reflected image of the eyeball by irradiating infrared rays and a second method using image processing exist.
As the first method, for example, a technique described in Japanese Patent Disclosure (Kokai) PH6-261863 is known. However, in this technique, the user feels great burden because the infrared ray is directly irradiated to the eyeball by a radiation diode.
As the second method, a technique described in Japanese Patent Disclosure (Kokai) PH4-225478 is known. In this second technique, the edge of the pupil is detected and the gaze is calculated by a center coordinate of the pupil. However, this technique is not stable for variation of illumination and it is necessary to calculate a face direction and position by another means.
As a method to solve the above-mentioned problem of the image processing, as shown in Japanese Patent Disclosure (Kokai) PH11-175246, a technique using a face area or a pupil area is known. In this additional technique, a stable method for detecting the gaze can be realized for variation of illumination or variation of head position. However, in this method, if the face area or the pupil area cannot be detected, a problem that the gaze direction cannot be detected exists.